Light diffuser actuator film (ldaf) keypad module

ABSTRACT

A keypad module which comprises a light diffuser actuator film (LDAF) and metal dome sub modular assembly for a total keypad solution that can overcome the shortcomings of the prior art, also being slim in thickness, consume less electrical energy as well as being easy to manufacture reducing the amount of involved human resources, consolidating plunger sheet and light guide film into one layer and also capable of providing a good tactile feel and an uniform luminescence on the key top, being properly applicable to telecommunication devices, remote controls, PDAs, car audios and controls etc as shown in FIG.  4.

FIELD OF THE INVENTION

The current invention relates to a keypad module for mobile phones, andparticularly to a keypad module provided with an incorporated LightDiffuser Actuator Film (LDAF).

TECHNICAL BACKGROUND

A mobile phone is a wireless communication appliance capable of allowingthe user to carry and use it. Such appliance may have diverse designs ofthe hand-phone terminal comprising bartype phones with exposed keybuttons, flip-type phones, fold-up type or swinging type compact mobilephones to improve further on the portability and outlook.

In addition, the hand phone includes a keypad assembly as input meansfor carrying out several wireless communication functions. The keypad isan assembly of individual parts, stacked up together, and has numericand alphabetical characters and/or symbols, which are depressed ortouched by the user.

A normal conventional keypad of the prior art is just an individualpiece of key top whereby it has a web to activate the tactile feeland/or have a separate actuator and/or plunger and metal-dome providingthe user with a tactile feeling.

The current plunger sheets have either limitation on the keypad heightand/or are restricted due to its mechanical properties, which result intoo many layers of components and/or difficulty to achieve the webthickness, due to manufacturing process constraints.

Therefore it is impossible to have even click ratio. In addition, thecurrent plunger sheet may not be able to offer good tactile feel,transmit input force from the key-top to the metal dome and to laminatethe key top as a single layer.

Also, the keypads of the prior art are not easy to manufacture and/orare not adequate for avoiding the tedious amount of mechanical errorsand do not allow a reduction of the human factor, because they areeither restricted by manufacturing process constraints.

In addition, the current keypad light up portion is provided by manylight emitting diodes (LED) and/or an electroluminiscent (EL) lamp. TheLED lighted up keypad view from the user provides inconsistentluminescent, this is due to the placement of the LED which is designatedat the specific location near the printed icons on the key top. Thiscreated hot spot to icons that is near to the LED, such concept requiresmany light emitting diodes (LED) to be mounted, resulting to high energyconsumption. The other alternative light source, EL Lamp providesuniform luminescent on the key top, but it is costly and/or consumingmore energy. Such EL lamp had shorter life spend, the printed dielectriclayer, provide the luminescence light, subject to user operatingpressure, result to the peeling of dielectric ink layer from the carrierfilm after a period of time.

Therefore, there is a need to provide a keypad module for mobile phoneswhich overcomes the shortcomings of the prior art, also being slim inthickness, as well as being easy to manufacture reducing the amount ofinvolved human resources, conserve less electrical energy by using lesslight emitting diodes (LED) for the key top luminescent, and mustprovide an uniform luminescence light up to key top icon from user'sview. The luminescent component must also be robust, able to withstanduser's operating pressure, also capable of providing a good tactilefeel, and even click ratio, importantly consolidating the light guideand plunger into 1 layer.

For the above purposes, the keypad module of the present invention isdisclosed—comprising a Polycarbonate (PC) and/or PolyethyleneTherephtalate (PET) film with moulded plunger on one side and/or with amicro dot structure or micro nubs form and/or screen printed on theopposite side and a metal dome sub modular assembly for a total keypadsolution that can diversify away from the current keypads and overcomethe shortcomings of the prior art. Such a keypad module is claimed inindependent claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the invention will now be provided withreference to the accompanying drawings in which:

FIG. 1 a shows a front view of a silicone rubber plunger of the priorart;

FIG. 1 b shows a cross sectional view of the silicone rubber plunger ofFIG. 1 a;

FIG. 1 c shows an enlarged view of detail A of the plunger of FIG. 1 b;

FIG. 2 a shows a front view of a silicone rubber key of the prior artwith actuator;

FIG. 2 b shows a X-X′ cross sectional view of the silicone rubber keywith actuator of FIG. 2 a;

FIG. 2 c shows an enlarged view of detail A of the actuator and/orplunger of FIG. 2 ab;

FIG. 3 shows a cross sectional view of a keypad with a normal actuatorstack-up;

FIG. 4 shows a cross sectional view of a keypad module of the inventionwith an inverted light diffuser actuator film (LDAF) stack-up;

FIG. 5 shows a cross sectional view of a keypad module of the inventionwith a normal light diffuser actuator film (LDAF) stack-up;

FIG. 6 a shows an exploded isometric front view of the Light diffuseractuator film (LDAF) and metal dome sub modular assembly;

FIG. 6 b shows an exploded isometric back view of the Light diffuseractuator film (LDAF) and metal dome sub modular assembly;

FIG. 7 a shows the Actuator side in isometric view;

FIG. 7 b shows a Dot Pattern side isometric view;

FIG. 8 a shows the Plunger side in detailed 2D view;

FIG. 8 b shows the Dot Pattern side in detailed 2D view;

FIG. 9 shows a cross sectional view of the Light diffuser moulded withactuator;

FIG. 10 shows a partial plan view of the Light diffuser moulded withactuator;

FIG. 11 shows an Isometric cross sectional view of the Light diffusermoulded with actuator;

FIG. 12 a shows the LED light energy only partially transmitted into thediffuser film due to the thickness of the film;

FIG. 12 b shows the LED light energy being fully absorbed into thediffuser film by the absorber.

DETAILED DESCRIPTION OF THE INVENTION

Making a reference to the prior art, FIGS. 1 a, 1 b and 1 c depict asilicone rubber plunger sheet (1) front view, a cross section view and adetail A, respectively. Referring to FIGS. 2 a, 2 b and 2 c, theydepict, respectively, a front elevational view, a cross section X-X′ andan enlarged view of detail A of a silicone rubber key with plunger (2),where the different elements forming the silicone rubber key withplunger (2) are shown in detail: a rubber keypad (22), light guide film(LGF) (23), adhesive (24), protective film (25), adhesive film (26) andmetal dome (27). This normal conventional keypad is just an individualpiece of a key top whereby it has a web to activate the tactile feeland/or have a separate plunger and metal-dome providing the user with atactile feeling. Regarding to FIG. 3, there are respectively shown across section view (3) of the prior art, where the different componentsof the light guide plunger are represented separately: metal mesh (31),mold-print plungers with island (32), stopper adhesive (33), Mylar domesheet (34), and metal dome (35).

According to the present invention, it is disclosed a preferredembodiment of a keypad module (4) (FIG. 4) for a mobile phonecomprising: a key-top layer 1 (41) with second surface printing; akey-top adhesive layer 2 (42) for bonding the key-top (41) to theadjacent layer; an actuator layer moulded to a light guide film (LGF)surface having a plurality of bosses (52) protruded from a positioncorresponding to movable contacts and a plurality of UltraViolet (UV)polymer or silicone rubber plungers, each disposed on the key top at aposition corresponding to each boss (52) and protruding from the LGF ata desired height, the alternate side of the moulded plunger, dotpatterns (51) are locally formed in specific regions, so that light isintensively supplied to the predetermined regions of the keypad (LDAF)layer 3 (43) through a light absorber (50); a LDAF adhesive layer 4 (44)to bond the light guide plunger to the adjacent layer; a dome Mylarlayer 5 (45) to locate metal domes at predetermined positionscorresponding to the plunger on top an ON/OFF circuit printed on aPrinted Circuit Board (PCB) and/or Flexible Printed Circuit (FPC); adome spacer layer 6 (46) for bonding the dome Mylar (45) to the PCBand/or FPC; a metal domes layer 7 (47), having a plurality of movablecontacts disposed on a printed circuit board (PCB, see below), each ofthe key tops being printed with numeric, alphabetical or symbolicdisplays of the key top to transmit light through the display; a printedcircuit board (PCB) and/or flexible printed circuit (FPC) layer 8 (48)having a plurality of stationary contacts; a light emission diode (LED)layer 9 (49) providing the light source to illuminate the key topthrough the light diffuser actuator film (LDAF) (43). The dot patterns(51) are formed by means of a thermoforming or printing process.

Another aspect to the present invention, (FIG. 5), the light guide filmplunger (43′) can be reversed with the micro dot pattern (51) directlyunder the key top, the plunger (52) directly on top of the metal dome(47).

FIG. 6 a further clarifies the LDAF (4) concept by showing an explodedisometric view of the preferred embodiment of the invention depictingfive layer which constitute the core of the invention: an actuatorco-moulded LDAF (43), a LDAF adhesive (44), a dome Mylar (45), a domepacer (46), and a metal dome (47). It is shown how the cites layer arestacked up from bottom (47) to top (43). FIG. 6 b represents a back viewof the elements of FIG. 6 a.

FIGS. 7 a and 7 b show, respectively, a front and a back isometric viewof the Light Diffuser Actuator Film (LDAF) (43), where is depicted theactuator surface at the front view and the dot pattern (51) at the backview.

FIGS. 8 a and 8 b show a 2D detailed view of the Light Diffuser ActuatorFilm (43) where there is represented, respectively, the plunger at thefront view and the dot pattern (51) at the back view.

According to further another aspect of the present invention, the lightdiffuser actuator film (LDAF) (43), (FIG. 9) of the present invention,is the most important layer on the whole module (4); it causes theincident light from the side light source, formed by the light emissiondiode (LED) layer 9 (49), to be surface emitted by the micro dot patternstructure (51) on the polycarbonate (pc) film, the UV and/or siliconemoulded plunger (54) on the alternate side of the micro structuregeometry also controls the ergonomic and tactile feel to the user.Additionally, dimensions B and C represent, respectively, the webthickness and the plunger height.

Still another further aspect to the present invention, a light absorber(50) (FIG. 4 & FIG. 5 can be moulded together with the plunger (43) justbeside the light emitting diode (49), the light absorber (50), absorbsthe maximum amount of light from the light emitting diode (LED) into thelight guide film, resulting to a brighter luminescence on the key top.

FIG. 10 shows a partial plan view of the Light Diffuser Actuator (4)where is depicted in detail a LED light source (49) and some actuators(53).

FIG. 11 shows an isometric cross sectional view of the Light DiffuserActuator (4) where there is represented a LED (49), the light absorber(50), the co-moulded UV layer (55) and one actuator (53).

FIGS. 12 a and 12 b illustrate a comparison between a normal light guidefilm thickness and the LGF of the invention provided with an absorber(50), where there is shown how the light rays are fully transmitted tothe LGF by the absorber (50) in the preferred embodiment of theinvention, whereas there is loss of light energy in other embodiments ofthe prior art.

Having described in detail the present invention, it will be obvious forany skilled in the art that modifications may take place regardingmaterials and arrangements without departing from the essence of theinvention, which is claimed below.

1. A keypad module (4) made up by stacking up the following layers: akey-top layer 1 (41) with a surface printing; a key-top adhesive layer 2(42) for bonding the key-top layer (41) to an adjacent layer; anactuator layer moulded to a light guide film (LGF) surface formingtogether a layer 3 (43); a light guide film adhesive layer 4 (44) tobond the light guide film to an adjacent layer; a dome Mylar layer 5(45) to locate a plurality of metal domes (47) at predeterminedpositions; a dome spacer layer 6 (46) for bonding the dome layer (45) toan adjacent layer; a metal dome layer 7 (47) having a plurality ofdomes, each dome provided of movable contacts; a printed circuit boardlayer 8 (48) having a plurality of stationary contacts; a light emittingdiode layer 9 (49) to illuminate the key-top (41) through the lightguide film (43); the keypad module (4) characterized in that said lightguide film (43) is provided with a plurality of bosses (53) protrudingfrom a position corresponding to said stationary contacts, a pluralityof plungers (54) at a positioning corresponding to each boss (53) and inthat the alternate side of said light guide film (43), dot patterns (51)are locally formed in specific areas.
 2. A keypad module (4′) accordingto claim 1, characterized in that the light guide film plunger (43′) isstacked up in reverse position with the dot patterns (51) directly underthe key-top layer (41).
 3. A keypad module (4) according to claim 1,characterized in that said layer 8 (48) is a Flexible Printed Circuit(FPC) having a plurality of stationary contacts.
 4. A keypad module (4)according to claim 1, characterized in that the light diffuser actuatorfilm (43) causes that incident light from the light emitting diode (49)is surface emitted by the dot pattern (51) to the plurality of mouldedplungers (54).
 5. A keypad module (4) according to claim 1,characterized in that said plurality of moulded plungers (54) provide anergonomic and tactile feel to a user.
 6. A keypad module (4) accordingto claim 1, characterized in that a light absorber (50) is mouldedtogether with the light guide film (43) just beside the light emittingdiode (49).
 7. A keypad module (4) according to claim 1, characterizedin that said light emitting diode (49) is a side-firing LED.